2002 F-150 4X4 5.4L
I have a check engine light and the faults are "system too lean for bank one and two" If forget the numbers at the moment.
Anyway I've checked around extensively for vacuum leaks and can find none. I've also cleaned the mass air flow sensor. I got to checking the EGR system today it all checks out except that there is no vacuum at the small hose going to the EGR valve itself at any time. I checked with the engine off idle at operating temp and there is zero vacuum. I have another truck just like it and tested it the same way and it has about 3" of vacuum under the same conditions. What gives?
I've verified that there is vacuum coming to the EGR vacuum control valve and the hose coming off the vacuum control valve going to the EGR valve will hold vacuum when I pull one on it with a pump. So do these control valves cause a system too lean fault? Or is it what controls the vacuum control valve causing this.

 

Wild goose chase. There is not supposed to be any vacuum at the EGR valve EXCEPT when the PCM commands the EVR solenoid to supply it. Since this is not supposed to happen in your driveway (it's only supposed to happen with a fully warmed up engine while driving at a steady state), it would appear the other vehicle actually has a leaky EVR solenoid.

Your fault codes are one of the most common subjects discussed here. A few moments with the SEARCH tool should get you plenty to read.

 

Yea I know that. That's why I was going down the road while I was testing it and not in my driveway.
Anyway, I replaced that vacuum solenoid and retested and now im getting vacuum when I should at it. Im going to check some more things today but hopefully that was the problem. That valve must have been causing a vacuum leak only when it was actuated by the pcm to operate the egr valve.

 

Not sure about the V-8,but my V-6 4.2 had a DPFE sensor.This sensor(if memory serves) is last in line before the EGR valve itself.Mine was bad,and throwing a code(dont remember the specific code) but it may be worth looking into.
The one on my 97 was metallic,and heavily corroded internally.The replacement was plastic,and it indeed solved my problem.I havent looked under the hood for one on my 07,but figure there is one somewhere under there.